router reboots itself once a day

Hi my router has been rebooting by itself once a day for around 4 weeks at similar time around 9.30 pm . It takes only 2 minutes for the reboot then everything is ok until 9.30 pm the next day .Ive been switched over from aol to talk talk recently and have my old aol router (THOMSON ST585v6sl ) .Ive had no problems what so ever in the past and my router settings are what ive always set them at .Ive contacted Talk talk they tested the line but nothing is wrong they say . I just find it very strange it only happens once a day ,ive formatted my PC and updated everything but still the same .Does anyone have any ideas what it could be ?